Electrical component



July 20, 1948. F. F. SYLVESTER 2,445,719

ELECTRICAL COMPONENT 4 Filed April 1, 1946 5 Sheets-Sheet 1 INVENTOR. Frederic/r E Sylvester July 20, 1948. RF. SYLVESTER 2,445,719

ELECTRICAL COMPONENT Filed April 1, 1946 5 Sheets-Sheet 2 l Fig.- 5

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F /'g.- 7 F reden'c/r E Sy/ ves/er y 1948- F.- F. SYLVESTER ELECTRICAL COMPONENT Filed April 1, 1946 5 Sheets-Sheet 3 INVEN TOR. Frederick E Sylvester July 20, 1948. F. F. SYLVESTER 2,445,719

ELECTRICAL COMPONENT Filed April 1, 1946 5 Sheets-Sheet 4 Bias Source g- INVENTOR.

F reoer/c/r Sylvester July 20, 1948. SYLVESTER 2,445,719

ELECTRICAL COMPONENT Filed April 1, 1946 5 Sheets-Sheet 5 Bias Source F/g' /2 3 F reaer/c/r F Sylvester Patented July 20, 1948 UNITED STATES PATENT OFFICE 12 Claims. 1

Simultaneous selection of piezoelectric crystals and adjustment of tuning element in electronic equipment is well known in the prior art as represented by the U. S. patents to Trogner, 1,609,- 744, dated December 7, 1926; Trogner, 1,727,575, dated September 10, 1929; Prochnow, 2,182,352, dated December 5, 1939; and Chandler, 2,382,203, dated August 14, 1945. With systems of these types, replacement of one or more crystals necessitates changes in the tuning element or its controls, an operation requiring the services of skilled technicians,

The prior art also teaches the use of a plurality of piezoelectric crystals, each provided with one or more separate and adjustable capacitors, wherein the capacitors are capable of being preset to resonate or tune a circuit comprising one or more coils, for selecting any one of a group of frequencies by manipulation of a particular push button or similar control.

It is likewise common practice to employ push button selection for tuning circuits incorporating a multiplicity of separate adjustable trimmer capacitors and fixed inductances where selector switches simultaneously switch two or more sets of trimmer capacitors to effect resonance at different frequencies with two or more inductance coils, as in a superheterodyne converter circuit. Most circuits of this general category employ two sets of trimmer capacitors and two coils, one set for the local oscillator circuit and one set for the antenna or radio frequency signal input circuit. There are also numerous modifications of such push-button converter circuits wherein piezoelectric crystals are not utilized, such as those employing a multiplicity of coils and a single fixed capacitor for each separate circuit with provision to adjust the inductance of each of the coils over a limited range for selection of a group of frequencies by push button switch selection of separate adjustable coils or adjustable capacitors.

Since the most carefully constructed trimmer capacitors and so-called slug-tuned coils (adjustable inductances), of the types in use with these prior art arrangements, are known to drift so appreciably over a period of time as to require repeated adjustment even in use with the broadcast frequencies (540 k. c. to 1600 k. c.) the problems attending the use of such agreements with frequency modulation and television frequency bands are even greater due to the presence of additional drift producing factors.

In accordance with the present invention these shortcomings of the prior art have been remedied to a great extent by combining as a unit, a crystal or frequency determining element which controls the oscillator tuning, and a stable fixed capacitor having a predetermined value-with respect to the crystal operating frequency for controlling various related circuits.

The broad combination of a piezoelectric crystal and capacitor constructed as a unit, is of course known, as exemplified by the U, S. patents to Tripp, 2,069,633, dated February 2, 1937; Fair, 2,260,707, dated October 28, 1941; and Usselman, 2,284,545, dated May 26, 1942. In each of these disclosures however, the relationships, both physical and electrical, between the crystals and capacitors are vastly different from those of the invention proposed herein, and therefore do not lend themselves to the same uses as contemplated by this invention.

Inasmuch as the inductance values of antenna and loop coils for broadcast receivers, as well as the tuning inductance range or curve of oscillators have been more or less standardized among the various manufacturers, this invention adapts itself quite readily to a mode of distribution of broadcast receivers, for example, where the equipment would be manufactured and equipped with all components except the crystal-capacitor units, which would be installed by local dealers in accordance with the frequencies required in their areas. Since the units are preferably assembled in cans or envelopes provided with projecting pins, it is merely necessary to press the pins into complementary sockets in much the manner that a vacuum tube is now installed. The provision of suitable gang switches in the equipment permits the accurate selection of a desired broadcast frequency by actuation of a single control element, which simultaneously interconnects the crystal and capacitor of a unit in proper relationship with their respective circuits.

The tuning unit contemplated may comprise a piezoelectric element of desired type and a capacitor having a predetermined value based upon the operating frequency of the crystal mounted in a container through which suitable leads are extended for interconnection of the crystal and capacitor electrodes in the circuits for which they are designed. The piezoelectric element or crystal and capacitor are preferably arranged in noninductive relationship and the container is p erably shielded or composed of shielding material.

Being generally desirable to effect electrical grounding of the container or envelope of the tuning nit, provision may be made to electrically connect any of the base pins serving as terminals for the elements within the container and the envelope itself; and in cases where the crystal or capacitor elements cannot be operated at ground potential due to particular circuit requirements, a separate base pin may be provided for electrically connecting the outer shell and any shielding means required within the tuning unit.

In some cases it may be desirable that the piezoelectric element. be--shielded or electrically iso lated from the. capacitor, electrostaticallyor elec-- tromagnetically or both. In cases where an electrode of either the crystal element or the capaci tor element or an electrode of each are at ground potential, the grounded electrode (or electrodes) is preferably that adjacent to the other element so as to provide a grounded shield between the two elements and their circuits. the crystal nor capacitor elements has an electrode at electrical ground potential, a metallic shield may be introduced between them in conduotive. relationship with the envelope.

The capacitor and crystal of each unit will have, definitely computedvalues, depending upon the application for which the unit is intended. Some of the relationships computed include: a capacity inversely proportional to the square of the algebraic sum of the crystal operating frequency? and a constant; a capacity inversely proportiona'l to the; square of the algebraic sumof the. crystalxoperating frequency and another frequency; a capacity inversely proportional to the square of the crystal operating frequency modified by'a' constant; av capacity inversely proportional to the. square. of the crystal operating" frequency modified by another frequency; and a capacity inverse'ly'proportional to the square of the crystaloperating frequency.

The applications of the crystal and capacitor incorporated in a single plug-in unit, in accordance with present invention, will be manifold; as contemplated herein, the frequency of the piezoelectric element and the value of the fixed capacitor. have a definite mathematical relationship. with respect .to one another for any given installation; and in each such installation, the substitutioniof a piezoelectric element of predetermined Oscillation frequency requires a capacitor. having predetermined characteristics-to be; associated with the related oscillating, fre- .quency, multiplying and/or amplifying circuits.

A more complete understanding of theinvennon willifoll'ow from a description of the attached drawing wherein:

.1V is a plan of a crystal-capacitor unit takenalong line l- -I of Fig. 2;v

Fig-2' is an elevation of the unit, partially in section, taken along line 2-2 of Fig. 1;

Fig. 3. is. an elevation, partially broken away, looking from the right OfiFig. 2; with theenvelope. removed Fig.-. 4; is. an. elevation looking from the left of Fig,.2-, with the envelope removed;

iEigs. 5. to are circuit diagram depicting typical applications. of the units to known types ofcircuits;

Ei'g;...11-'.is.a circuit, diagram incorporating a plurality. of? units andswit hins ra nts; an

Fig. 1.2; another circuit diagram incorporating the new units and. Switches.

'Ineunit depicted in Fig 1' to 4 comprises a. baseZ2' ofthermoplastic or thermosetting di electric material into which a plurality of terminal-pills are molded in interlocking. and pres.- s'uretislit relationship. Two f the pins 24 are provided for connection with the crystal elec- Where neither trodes, while the other two pins 26 are connected with the capacitor electrodes. Each pin is provided with an intermediate collar 23 serving to anchor it in the molded base. As clearly shown in Fig. 4, the base is stepped to define a shoulder 30 in the radial face of which is formed an annular groove or depression 32 to serve as a seat for a volumetric sealing gasket 34 of rubber-like properties, whichisi deformed. from its original condition dppiotedirr Fi 3213.0 the approximate shape shown in Fig. 2 upon assembly of the unit. The lower surface of the base and its periphery are preferably joined by a fillet or groove 36 for co operation with the envelop upon assembly.

Upon the upper portions of the terminal pins 24 and 26 resilient mounting clips 38 and ill for the-crystal 42': and capacitor 46, all respectively, aroprovided. Each of these clips is secured to its terminal pin by a welded or soldered joint to assure adequate physical and electrical connections forpro'pr pertormanceinoperation.

crystal 4 2 is shown as having opposed electrodes it and 4B evaporated orotherwise applied as; electricallyconducting coatings, the electrode 46 beingshown" in Fig. 3 as having a tab 50 extending'over the upper left edge of the proximate face'ofthecry's tal and terminating at the base of the bevel onthe remote face, for electrical connection withthe upper portion of the left hand clipta the electrode 4-8 being shown as having a tab- 52 extending over the upper edge of the remote face of the crystal and terminating at the base-ofthe'bevel on tlie proximate face, for electrical connectionwith the other of the clips 38. Eachof? the clips 38. is formed from wire to form a structure which. is somewhat channel-shaped in elevation; Fig-'2, having-a web-54., apair of opposed reentrant'flanges' 56', and a. loop 58 bent or twisted from theplane-of the web to'form a suitable number of turns for embracing the upper portions or the terminal pins 24, to" which they are-bonded electrically-and mechanically by welding orsol'der Ell The capacitor i i, also provided with opposed electrodes 62 and fidwl'i'ich may be applied as electricall'y conducting coatings is received by the clips-4U; each clip being inphysi'cal and electrical contact with one of the electrodes. The dielectric body 66 has its proximate electrode 64, as viewed in- Fig: 4, discontinued at the lower left corner to avoidcontact' with the left hand clip ill. similarly, the remote electrode 62 is applied to clear the lower right hand corner of the dielectric body; as indicated in" broken lines, to avoid contact with' the right hand clip 18. Thus the right hand clip, still referring to Fig. 4, engages the proximate electrode and the left hand clip the remote electrode; the contacts in each case being completedbya soldered or cemented'joint 6i.

Each of the capacitor clips Ml is formed from a single blank of resilientmetal and comprises a split socket 68 for embracing its terminal pin 26 to which it is secured by solder or Welding iii. The capacitor engaging; elements include a bowed resilient leaf i2 and a substantially erect leaf M, which define an outwardly divergent jaw'to receive the capacitor.

Withtheparts thus assemhl'ed,the envelope l8, whichis shielded or which is itselfa shield, both electrostatic-and electromagnetic, is applied to the base and; secured thereto ihpressuretight rela tionship. The envelope may have. a generally cylindrical or frus'tro-conical body formed with a c1osedupper'end82 and .an open lower end. Towards its" open end, the envelope is enlarged to define an outwardly directed shoulder 84 and a downwardly depending skirt 85. When the envelope is applied to the base, its shoulder 84 deforms the gasket 34 causing it to flow into the groove 32 to effect a seal, whereupon the lower edge 8'! of the skirt 88 is rolled or crimped into locking relationship with the base at its fillet 3B.

In order to maintain one or more of the crystal and/or capacitor electrodes at a common potential with the envelope and/or with one another, thin conductive metal strips 88 may be afiixed to the terminal pin or pins involved, at a convenient point such as the soldered or welded joints between such pins and their clips. The lower ends 89 of such strips 88 will trail over the upper portion of the base and gasket, down along the periphery of the base. Then when the envelope is applied and crimped, electrical contact will be established between the envelope and the one or more strips. Adjacent electrodes of the crystal and capacitor have been depicted in Fig. 2 as interconnected with the envelope to maintain them at common potential, but it should be understood that certain applications of the unit may require other arrangements in this behalf, including omission of the grounding entirely. In applications of the unit where the envelope or shell 18 should be connected to electrical ground and Where it is not desirable to ground any portion of the crystal or capacitor elements, an additional terminal pin 9| (Fig. 1) incorporated in the base 22 will serve to ground the envelope through a conductive metal strip 88 which may be afiixed to the pin 9| by Welding or soldering and to the envelope in the manner previously described.

In cases where it is necessary to electrically shield the crystal element from the capacitor and neither element is to be electrically connected to ground, a metallic shield or plate 93, is interposed between the crystal and capacitor to engage the inner wall of the shell or envelope l8, and be retained therein by a resilient forced fit established by compression of its bent fingers 95, against the inner wall of the envelope and located by means of suitable slots formed in the upper surface of the base 22 with which the lower edge of the shield registers during assembly of the envelope upon the base. Location of shield 93 in these slots causes it to assume a position in a plane substantially parallel with respect to the crystal 42 and capacitor 44. and substantially equidistant with respect thereto. Electrical connection of the shield to ground is thus effected through the fingers 95, envelope l8, connecting strip 89, and terminal pin 9 I.

A Miller oscillator embodying the crystal-capacitor units of the present invention is de picted in Fig. 5. Whereas only one such unit has been illustrated, the unit terminals have been drawn to indicate adjustable taps relating them to the remainder of the circuit, whereby the taps may be shifted simultaneously to connect with terminals of any number of such units having different constants. This circuit is representative of a type of crystal controlled oscillation generators, for which it is desired to establish the relationship between the operating frequency f2 of the crystal 42 and the value C1 of the capacitor 44.

Where )2 is the operating frequency of the crystal unit; and is is the output operating frequency of the tuned resonant oscillator circuit;

where n is an odd whole number. L is the plate circuit inductance having a fixed value of A henries; and C1 is the capacity of the capacitor 44. At resonance,

1 21rf L f3 C1 1 1 4x25}; Substituting for I 412 a constant K1 or in terms of f2 This relationship may be expressed as a capacity inversely proportional to the square of: the crystal operating frequency modified by a constant.

With regard to the Tri-tet oscillator shown in Fig. 6, it may be said to represent harmonic-generating crystal oscillators to which units 20 may be applied to advantage. Here again only one unit has been shown, but with terminals indicated as shiftable from one such unit to another to vary the frequency characteristics of the circurt.

Where is is the resonant frequency of the crystal 42, and is the operating frequency of the tuned resonant circuit L, C1, assuming a high reactance of L at such frequency, L can be neglected in determining the value C1 of the capacitor 44 in terms of f2.

as in the preceding case.

But in this circuit, in general is is slightly higher than f2 by a value Af suilicient to assure stability under varying load.

Hence, since L is constant for a given circuit, and K1 is the same as in the previous case,

or the capacity is inversely proportional to the square of: the crystal operating frequency modified by another frequency.

Fig. 7 of the drawing illustrates the use of the unit of the present invention in tuning a singleended converter tube in a superheterodyne receiVel'. Here again, the circuit connections with the unit are indicated as readily shiftable to other units of the same type for operation at other frequencies. In this case I1 is the incoming R. F. carrier frequency, f2 or fz the local os- CillEttOI' operating frequency established by the crystal 42, and f3 the intermediate frequency. The antenna coil secondary or loop inductance L is assigned a constant value of A henries.

The values of f2 and fz are selected to produce the relationships f2 +fs=h and f2f:s=f1

Now considering the resonant circuit containing the inductanceelr and theec-apacitorr 4:41 havingwai capacitance-C1 C 1 1 arL m 41r .A f Since is constant, it may be represented by K1 wherep n substituting for f1 K1,; Wt-m new)? and since in a partioul'ar circuitfais: a constant; the capacitance Ci can: be said to be inversely proportional to -the square of; the algebraic'smn' of the" cryst'al operating frequency and: a con-- stant';

A Colpitts oscillator: adapted to employany number of the units of the present invention is shown iniFi'g. 8 as connected with oneasuchiunit with shif t'able leads which can be connected w-ith other such units asdesiredi Where-fa is the opcrating frequency of the crystal 42 and" f3 the operating irequency'of the resonant; circuit-in cluding the capacitor 44' whose capacitance is 01, and an inductance L having a fixed value of A henries, it may be assumed that At resonance, as in previously discussed: examples;

and since fz=fa Hence, it may be said that the capacity is in- Versely proportional to the square of. the crystal operating frequency.

In the Pierce: oscillatordepict'ed in Fig; 9', ,se lecti'on of desired units is again indicated; The value C1 of the capacitance, id must be smaller at higher frequencies because lower values of' feedback coupling are required at higher frequencies. L is an inductance whose value is such that it will not resonate at the crystal frequency. Since. it is desirable that the plate load' be capacitivev at the crystal operating frequency,.it' will follow. that, the value ofCi will'be dependent, upon variable factors other than the crystal operating frequency. This example illustrates a situation in, which. the circuit design should be established prior. to a computation of the crystal-capacitor relationship.

Applications of the present unit to any composite triode-pentode converter, such as the pentagrid converter, heptode converter, hexode converter, or octode converter, are represented by; Fig; 10., where again,, any desired-1. numberof the circuits. by appropriate switching from the terminals of; the. single .unitindicated to corree spending terminals, of other units having desired constantse- The relationship ofthe value of. cat. pacitori 44 ((31),- and the frequency. of crystal. 42. (fz);is;i.analog;ous to that developed for the-circuit illustrated inFig. 7, namely, the capacitance is inversely proportional to the square of thealgee braicsumof the crystal operating frequency. and a.,constant;,

Fig; 1-1;.illustrates the. application of a plurality ofthe units: to a-superheterodyne receiver using asingle-endedconverter tube. The five unitslfl and,their-corresponding gang switches 90, 92,84, Sit-sand.-ilcxare-arranged for selectively introducing the-units intothecircuits for attaining a pushbuttontuning, which. requires no adjustment either -at the time 'ofinstallation or subsequently. There isalsoprovided a switch ltiiw-hose depression will establish circuitsfor. manuallytune ingthe receiver, independently of the crystal capacitor-units. The switches are of a known commercial type-wherein depression of any one buttonwill eject any of the others w-hichimay have been depressed previously. Such a receiver will;be'ad apted.,for push-button tuning of a predetermined group c-f transmitted frequencies (fivein the case illustrated) by introducing the terminalpins of units corresponding-tosuch frequencies into sockets, such as those produced for usewith miniature tubes, with reference to which, thenumbers l, 3, 5 and? have been appliedto the uppermost unit ofFig. 11.

Fig. 12'represents a similar circuit utilizing six units of, the-present invent-ion cooperating with six gang switches adapted for tuning six predeterminedfrequencies by the actuation of pushhut tons in: the manner. described with reference to Fig; 1-1. In thisaar-rangement, there isno-prov-isionof manualtuning; the sixth switch |fl2-having been substituted for the manual. tuning switch" Hill: ofFig. 11.

The-arrangements illustrated in Figs. 11 and-12 will'readily-adapt themselves to an entirely new mode of distribution of radio receivers. The manufacturer can ship the receivers without the tuning units to any distributor regardless of'geographicallocation. The distributor will maintain a stock of the units of the present invention suited tot-he needs of his particular area. Then to adapt the receiver to the broadcast frequencies desired by a given customer, the distributor need only insert the appropriate units corresponding to the desired frequencies without need for adjusting any'compcnents then or in the future.

No-eifort has been made to exhaust the various applications of the invention in describing the few illustrative examples in the foregoing description. Accordingly, these examples should not be construed as limiting the invention beyond the scope of the appended claims.

I claim:

1. Atuning unit comprising a piezoelectric element and a fixed. capacitor having a predetermined value based upon the operating frequency OIL the, element, mounted -in substantially non-in.- ductive relationship in a closed container, and leads for said element and capacitor extending through. said container.

2;, Atuning unit. comprising a piezoelectric element and a fixed capacitor having a predetermined value based upon the operating frequency of the element, mounted in substantially non-inductive relationship in a sealed container provid ing shielding, and leads for said element and capacitor extending through said container.

3. A tuning unit comprising a piezoelectric element and a fixed capacitor having a predetermined value based upon the operating frequency of the element, mounted in substantially non-inductive relationship in a closed shielding container, and leads for said element and capacitor extending through said container.

4. A tuning unit comprising a piezoelectric element and a fixed capacitor having a predetermined value based upon the operating frequency of the element, mounted in substantially non-inductive relationship in a closed container providing shielding, said element and capacitor having adjacent electrodes connected to said shielding, and leads for said element and capacitor extending through said container.

5. A tuning unit comprising a piezoelectric element and a fixed capacitor having a predetermined value based upon the operating frequency of the element, mounted in substantially noninductive relationship in a closed container, means electrostatically shielding said element from said capacitor, and leads for said element and capacitor extending through said container.

6. A tuning unit comprising a piezoelectric element and a separate capacitor having a capacity inversely proportional to the square of the algebraic sum of the element operating frequency and a constant, mounted in a closed container, and leads for said element and capacitor extending through said container.

7. A tuning unit comprising a piezoelectric element and a separate capacitor having a capacity inversely proportional to the square of the algebraic sum of the element operating frequency and another frequency, mounted in a closed container, and leads for said element and capacitor extending through said container.

8. A tuning unit comprising a piezoelectric element and a separate capacitor having a capacity inversely proportional to the square of the element operating frequency modified by a constant; said element and capacitor being mounted 4 9. A tuning unit comprising a piezoelectric element and a separate capacitor having a capacity inversely proportional to the square of the element operating frequency modified by a preselected frequency; said element and capacitor being mounted in a closed container, and leads for said element and capacitor extending through said container.

10. A tuning unit comprising a piezoelectric element and a separate capacitor having 2. capacity inversely proportional to the square of the element operating frequency, said element and capacitor being mounted in substantially non-inductive relationship in a closed container, and leads for said element and capacitor extending through said container.

11. A control system for oscillator circuits comprising matched piezoelectric element-capacitor units corresponding to predetermined frequencies, the capacitor of each unit having a predetermined value based upon the operating frequency of its element, each of said elements and capacitors of a unit being mounted in substantially non-inductive relationship in a closed container, leads for each of said elements and capacitors extending through its container, and means for selectively interconnecting said units in said circuits.

12. A control system for oscillator circuits comprising matched piezoelectric element-capacitor units corresponding to predetermined frequencies of diiferent values, the capacitor of each unit having a predetermined value based upon the operating frequency of its associated element, leads for each of said elements and capacitors, and means for selectively interconnecting said units in said circuits.

FREDERICK F. SYLVESTER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 5 Number Name Date 1,833,966 Fetter Dec. 1, 1931 1,994,228 Osnos Mar. 12, 1935 2,171,243 McKesson Aug. 29, 1939 

